1. Field of the Invention
The present invention relates to concrete masonry units (CMUs) that are united to form structures. The CMUs are generally prepared by placing a mixture of concrete, aggregate, water, and sand into a mold, compacting the mixture in the mold, and then drying it.
More specifically, the present invention relates to CMUs that incorporate a thermal insulating material therein, which are hereinafter referred to as insulated concrete masonry units (ICMUs). Most specifically, the present invention relates to ICMUs having heat bridges of relatively low density and minimal size.
2. Description of the Prior Art
Numerous attempts have been made in the prior art to provide a practical ICMU. When the walls of a structure are constructed with conventional CMUs, a secondary operation of providing the walls with insulation is necessary if the interior of the structure is to be economically maintained at a temperature different from that existing on the exterior of the structure. This second step of insulating the walls requires additional materials and labor which causes a large increase in the cost of building the walls of the structure. A practical ICMU is desirable because it eliminates the need for this second insulating operation.
Where ICMUs are used, there is a significant dollar savings in the cost of building the finished walls of the insulated structure. The labor involved where ICMUs are used is virtually the same as is required where conventional noninsulated CMUs are used, i.e., the ICMUs are put in place one-by-one and are secured to each other by surface bonding or a mortar of some type. The increased cost of an ICMU over a noninsulated CMU is not substantial when compared to the cost of the labor for the second insulating operation that is required where noninsulated CMUs are used. With this economic motivation, various attempts have been made to provide the art with a practical pre-formed ICMU.
The following is a brief discussion of selected prior art.
U.S. Pat. No. 4,027,445 discloses an ICMU. It is of conventional structure, and comprises two end walls, two side walls, and a mid-wall extending from one side wall to the other at a point approximately equidistant between the two end walls. First and second insulating inserts, formed of a lightweight foraminous heat insulating and fire retarding material, are provided in a shape that is adapted to be inserted into the two cavities in the structure of the CMU. These insulating inserts are first formed in a mold of some type and allowed to harden. The inserts are then inserted into the cavities in the CMU. Thus, the ICMU of this patent is formed by a three-step process: making the CMU, making the insulating insert, and then inserting the insulating insert into the CMU. The insulating inserts do not provide insulation across the entire side wall face of the ICMU. The insulating zones are interrupted by the thick load-bearing mid-wall and the two end walls.
U.S. Pat. No. 3,292,331 discloses interlocking blocks that form a wall construction. The block may be a CMU or may be formed of plastic (column 2, line 13). FIG. 4 of this patent illustrates a modification of the block unit that is provided with longitudinally disposed passages which are adapted to receive a slab of insulating material. This slab of insulating material provides an essentially continuous insulation zone across the side wall face of the block. However, the block is virtually a solid piece, which greatly increases its weight. This increased weight increases the cost of transporting and handling the block and requires that the static structure be provided with a stronger foundation because of the increased weight of the walls themselves. The blocks of the patent are not provided with a balanced handhold for masons, and cannot be laid in a running pattern (i.e., each course of block offset by 50%), which is stronger than the stacked pattern shown in FIG. 1 of the patent. Furthermore, according to the design of the block shown in FIG. 4, this block cannot be fabricated in a conventional block production facility.
A commercial product known and advertised as the Waukesha Insulation Block is an ICMU wherein the insulation zone is not interrupted by a thick midwall connecting the side walls. However, the insulation zone does not extend the full length of the side wall because the thick load-bearing end walls prevent it from doing so.
A proposed commercial product, advertised as the Thermoblock, is provided with a series of insulating pockets that extend along the face of each side wall. These insulating pockets provide an insulation zone that extends along each side face and is interrupted only by relatively thin load-bearing walls in between the insulation pockets. However, these relatively thin walls in between the insulation pockets have proved to be a major detriment to the use of the Thermoblock. They are insufficient to meet the load-bearing requirements of CMUs that are recognized in the art as those needed to comply with the ASTM C-90 standards.
West German Offenlegungsschrift No. 27 37 012 discloses a heat and noise insulating hollow brick comprising a thin outside layer and a much thicker inner load carrying part. It does not appear to be provided with a balanced hand hold for a mason and is designed to be laid in a stacked pattern (as shown in FIG. 3 of the Off.) rather than a running pattern. Furthermore, its obviously large size and weight would be detrimental to conventional block transportation and erection techniques.